I have my library moved to a 32GB external SD card.
After Dingo, this is what happens after I put the edge on 'standby' (close edge while still running).

After I 'wake up' edge by pressing menu button, i get the message 'SD card removed unexpectedly'. Then it goes through the 'SD card inserted etc etc..' This is followed by my reader app restarting (I see the edge image with books that you see while the edge boots).

Once the SD card was not 'found' again and I had to take it out and reinsert it.

Once, edge checked the SD card for errors (a new function??) after it was 'found' again.

I have now seen this whole thing happen at least 5-6 times in a row. I once put the edge to 'sleep' with nothing open on the reader side and I did not see the error, so must be something to do with the reader app.